An example of methods for producing bioethanol using cellulose-based biomass as a raw material is an enzymatic ethanol production technique of enzymatically hydrolyzing at least one of cellulose and hemicellulose.
In the case where a solution (hereafter referred to as a “saccharified solution”) containing saccharides containing glucose as a main component is produced by enzymatically degrading biomass and then ethanol is produced, a high-concentration saccharified solution with a saccharide concentration of 150 g/L or more needs to be produced. This is because if the saccharide concentration is 150 g/L or less, the concentration of ethanol obtained by fermenting the saccharified solution decreases, and thus a large amount of energy is required when the ethanol is condensed by distillation.
In a known method for producing a high-concentration saccharified solution, however, a large amount of biomass is charged into a reaction vessel and degraded with an enzyme (e.g., refer to PTL 1).